Magnetic Loading Techniques And Its Applications In High-pressure EOS

With the rapid development of pulsed power technology in the past20years, The experimental technique of magnetic driven loaded techniques has become an important means to study the dynamic characteristics of materials under high pressure. Recently, an n-shape structure of parallel plate electrodes is widely used. The pulse current flows in the opposite direction in the two electrode plates, while smoothly rising magnetic pressure is generated by the interaction of magnetic field caused by the current of one electrode plate and the current caused by another electrode plate. As a new experimental technique between the quasi-static load and the impact load, it can load multiple samples or flyers simultaneously. One experiment can provide the quasi-isentropic reference line of sample from tens of Kbar to several Mbar, the speed of launched macro aluminum flyer has reached45km/s. the response data of material under magnetically driven quasi-isentropic test is of great importance to check the material constitutive model and the equation of state, and is also an important application for the kinetic properties of the material, weapons physics, high energy density physics and astrophysics.It is of great significance for improving the load capacity based on the property of device to get more accurate experimental data, while more valuable high-pressure data of state equation is needed with the application of magnetic driven loaded plate. The off-Hugoniot data obtained by quasi-isentropic load is essential for calibration of the state equation, the uncertainty of the data determines its validity and application. Reducing the uncertainty of access of data in many ways is the key technology for the application of magnetic driven loaded technology to the state equation of material research. This work starts from the optimization design of load configuration, the current pulse shape technology, a number of coupled diagnostic techniques, the simulation of experiment state of magnetic driven loaded, the data processing methods and applications, analyzes the intrinsic uncertainty and measurement uncertainty possible present in the experiment and data processing, and presents and verifies the program of reducing the uncertainty of experiment data, carries out the research of magnetic driven loaded experiment technology from simulation to design, experiment diagnosis to analysis, the ability of load to application direction gradually.The main contents of this paper include:(1) The optimization design of magnetic driven loaded area.To meet the requirement of plane of the magnetic drive, uniformity and synchronization, the optimized parameters of loaded area is obtained by iteration calculation from the initial configuration of the magnetic field distribution, and the simulation of distribution of the static magnetic field is carried out. Where, the uniformity and synchronization of magnetic driven load is a major source to obtain uncertainty of experimental data.(2) The research of current waveform control technologyFirstly, according to the requirements of physical experiments, the ideal current waveform under the experimental requirement is calculated based on the reference of SESAME state equation database of related electrode and the sample material. After that the calculation of multi-branch pulsed power generator is carried out by coupled load parameter circuit simulation software to determine the appropriate convergence programs to achieve optimization and adjustment of magnetic driven current and to obtain experiment data of high accuracy.(3) The research of various diagnostic coupled techniquesTo obtain the experiment information under powerful magnetic field and high pressure loads, load current is the first diagnostic data. In addition, the measurement of speed-time history and wave profile is mainly carried out by non-contact measurement technique, while the related diagnostic is carried out by Doppler pins system(DPS), Optic-microwave mixing velocimeter(OMV) and line VISAR imaging techniques. To coupling all the diagnostic data, time schedule control system was performed in all experiments.(4) Numerical simulation of the experimental status of magnetic drive load plateThe dynamic magnetic field and distribution of current in the loaded area are calculated by MHD combined with drive current and load configuration. Which accurately predict the experimental condition and guides the direction of the load design (launch of high speed flyer, the compression of magnetic driven quasi-isentropic sample, high-speed collision of flyers, etc.) In addition, It improves the efficiency of the physical experiments a lot by the improvement of analysis of data and program of experiment guided by the simulation program after calibration and correction.(5) The methods of experiment data processingThe data processing mainly includes the processing of velocity interferometer signal and speed information from experiment measurement, the calculation from waveform profile information to state equation of material. This work focuses on the analysis of uncertainty caused by in terms of ways, such as data processing method, the load processing and diagnostic coupled techniques, etc. Finally, achieving the needs for check of the state equation by improvement and obtaining the uncertainty data of state equation.(6) The application to the high-pressure state equation of materialBased on the output characteristics of the device, the launch experiment design of high-speed flyer are carried out, the lunched speed of10mm0.725mm Ly12aluminum flyer reaches over11.5km/s. In addition, the optical properties of LiF window materials under quasi-isentropic compression are also investigated. The refraction factor and interface speeds of LiF window material are also calibrated until the quasi-isentropic compression pressure of50GPa. Thus it carries out the measurement of the speed of the historical sample/LiF window interface, and obtains the reference line of aluminum and tantalum.In this work, based on the output characteristics of the device, it carries out the research of magnetic driven loaded plate experiment technology, forms a design method of load structure, size and current waveforms, combined with numerical simulation of the experimental status, which can be used to guide the experimental design. In addition, a number of coupled diagnostic techniques are developed, and more valuable high-pressure state equation data are obtained through the improved data processing methods. Preliminary results obtained confirms that the experimental technique based on magnetic driven loaded plate pulsed power devices of multi-branch pulsed power devices has broad application prospects in the study of high-pressure state equation of material.